Natural Resources
Conservation Service
Ecological site R023XY606OR
SHRUBBY PUMICE PLAINS
8-11 PZ
Last updated: 4/10/2025
Accessed: 04/20/2026
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Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
Ecological site concept
Currently there is only a draft of the initial concept for this ecological site. The initial concept for this site places it within the Clayey Mesic Plateaus 8-14 PZ Wyoming Big Sagebrush and Thurber's Needlegrass Ecological Site Group. To view the General STM and other information available for this ESG please go to https://edit.jornada.nmsu.edu/catalogs/esg/023X/R023XY909OR
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
This site occurs on very broad low ridges in large basins and on old lake terraces at the edge of basins, often associated with gentle toe slopes below rims or ridges. Slopes range from 0-20%, but are typically 0-3%. Elevations range from 4300 to 4800 feet.
Table 2. Representative physiographic features
Landforms (1) Basin floor
(2) Ridge
(3) Terrace
Elevation 4300 – 4800 ft Slope 0 – 20 % Aspect Aspect is not a significant factor Climatic features
The annual precipitation averages 8-11 inches, most of which occurs during the months of October through March. The mean annual air temperature is 48 degrees F. Temperature extremes range from 110 to -30 degrees F. The period for optimum plant growth is from April through early June. Some fall growth can occur during October and November if these months are unusually warm and moist.
Table 3 Representative climatic features
Frost-free period (average) 90 days Freeze-free period (average) 120 days Precipitation total (average) 10 in ">Influencing water features
Soil features
The soils of this site are typically deep or moderately deep, somewhat excessively drained and loamy sandy or gravelly loamy sand in texture. They are generally formed from wind deposited volcanic ash/pumice and gravelly lacustrine deposits. Permeability is rapid to very rapid and the available water holding capacity for the soil profile is 3 to 7 inches.
Table 4. Representative soil features
Surface texture (1) Loamy sand
(2) Gravelly loamy sand
Family particle size (1) Sandy
Drainage class Somewhat excessively drained Permeability class Rapid to very rapid Soil depth Not specified Available water capacity
(0-40in)3 – 7 in Calcium carbonate equivalent
(0-40in)2 % Electrical conductivity
(0-40in)Not specified Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7 Ecological dynamics
The potential native plant community is dominated by mountain big sagebrush, antelope bitterbrush, and needleandthread. Thurber needlegrass, bottlebrush squirreltail, and Indian ricegrass are the other prominent grasses along with Ross Sedge. Other shrubs common in the stand are gray rabbitbrush and low green rabbitbrush.
Basin big sagebrush replaces mountain big sagebrush at the eastern edge of its range or warm droughty locations. Idaho fescue is present in small amounts at moist locations or positions, especially where transitional to Idaho fescue communities.
Needleandthread is a decreaser under heavy grazing pressure by cattle or horses. Ricegrass and Thurber needlegrass also decline with overgrazing. Excessive browsing of bitterbrush over several seasons will reduce plant vigor/production and eventually reduce the stand. Invaders such as cheatgrass, cryptantha, salsify and mustard may enter low condition areas. Fire kills or severly damages big sagebrush and bitterbrush, while stimulating the recovery of rabbitbrush through resprouting. Early summer burns cause high mortality in needleandthread, but much less or little in late summer or fall. Thurber needlegrass suffers high mortality from burns throughout the summer.State and transition model
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityHCPC
Figure 1. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Grass/Grasslike 500 575 650 Shrub/Vine 300 350 400 Forb 50 75 100 Total 850 1000 1150 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 178–345 needle and thread HECO26 Hesperostipa comata 144–288 – western needlegrass ACOCO Achnatherum occidentale ssp. occidentale 29–40 – Thurber's needlegrass ACTH7 Achnatherum thurberianum 5–17 – 2 34–82 Indian ricegrass ACHY Achnatherum hymenoides 12–29 – squirreltail ELEL5 Elymus elymoides 5–17 – Idaho fescue FEID Festuca idahoensis 5–12 – beardless wildrye LETR5 Leymus triticoides 6–12 – bluebunch wheatgrass PSSPS Pseudoroegneria spicata ssp. spicata 6–12 – 3 12–29 Ross' sedge CARO5 Carex rossii 12–29 – Forb4 10–27 common yarrow ACMI2 Achillea millefolium 1–3 – rockcress ARABI2 Arabis 1–3 – Indian paintbrush CASTI2 Castilleja 1–3 – Douglas' dustymaiden CHDO Chaenactis douglasii 1–3 – common woolly sunflower ERLAG Eriophyllum lanatum var. grandiflorum 1–3 – phacelia PHACE Phacelia 1–3 – Cascade knotweed POCA9 Polygonum cascadense 1–3 – fleabane ERIGE2 Erigeron 1–2 – woollypod milkvetch ASPU9 Astragalus purshii 1–2 – milkvetch ASTRA Astragalus 1–2 – Shrub/Vine5 92–212 mountain big sagebrush ARTRV Artemisia tridentata ssp. vaseyana 35–70 – antelope bitterbrush PUTR2 Purshia tridentata 35–70 – yellow rabbitbrush CHVIS5 Chrysothamnus viscidiflorus ssp. viscidiflorus var. stenophyllus 7–18 – rubber rabbitbrush ERNA10 Ericameria nauseosa 7–18 – Interpretations
Animal community
Livestock- This site is suited for spring grazing by cattle and horses under a planned grazing system. Needleandthread, Thurber needlegrass and Indian ricegrass are the key speices for management in high condition stands. After maturity of needleandthread, the sharp needle-like seeds can cause mouth injuries to livestock.
Wildlife- This site is commonly used by rabbits, rodents, and assorted variety of birds and their associated avian and terrestrial predators.Hydrological functions
The soils of this site have a high infiltration rate and a low runoff potential. The hydrologic cover is good when ecological conditionis high. The hydrologic soil group is A.
Supporting information
Contributors
C Tackman
Approval
Kendra Moseley, 4/10/2025
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) Contact for lead author Date 04/20/2026 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
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Perennial plant reproductive capability:
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